Reference may be made to the following U.S. Pat. Nos. of interest: 3,494,096; 3,653,177; 4,216,638; 4,219,988; 4,430,845; 4,494,362; 4,924,659; 4,939,889.
Presently available packaging machines for wrapping articles in a heat shrinkable thermoplastic film incorporate some type of film forming apparatus receiving a sheet of film from a roll and forming the sheet into a generally open tubular form to receive the article. The film tube is then heat sealed around the article with side sealer and end sealer mechanisms in a manner which is appealing to consumers.
Typically, a sheet metal film former conforming to the article being packaged is fabricated of sheet metal plates and is utilized to receive and form the tube of sheet material from the roll. Upon changing of the article size, a new custom-made sheet metal former must be fabricated to accommodate a new sized article so as to form the proper tube of sheet material required for packaging the article. This film forming apparatus requires separate individual custom-made sheet metal film formers for each article size required to be packaged.
Several different systems have been proposed to accomplish film forming for different sized articles. However, such prior systems require substantial adjustments or replacements of components in the packaging machinery, such as adjusting the side sealer mechanism pulling the film through the machinery or require a complete replacement of the film forming mechanism, similar to the custom fabricated film forming units.
Further, it is desired to utilize rolls of unfolded film, rather than rolls of center-folded film, since the rolls of flat unfolded film usually cost substantially less than the rolls of center-folded film. However, in forming the tube of film required to receive the article, many packaging machineries utilize center-folded film, either initially, or incorporating a folding mechanism to convert unfolded film to center-folded film. This, of course, requires additional machinery and increases the cost of the packaging machine.
It is desirable therefore to provide a film forming apparatus which is adjustable to accommodate several different sizes of articles to be packaged, and which can utilize rolls of unfolded plastic film directly without the need to initially form a center-folded sheet from the unfolded film.